Magazine type magnetic recorder



Nov. 8, 1949 H. NYGAARD I MAGAZINE TYPE MAGNETIC RECORDER 5 Sheets-Sheet 1 Filed A i-il 16, 194'! Y NVENTOR HER/346W N YG/M FD r M Ma ATTORNEY Nov. 8, 1949 .H. NYGAARD MAGAZINE TYPE MAGNETIC RECORDER 5 Sheets-Sheet 2 Filed April 1e, 1947 uvmvrm HER/MN A/ YG/MRD ATTORNEYS 1949 H. NYGAARD MAGAZINE TYPE MAGNETIC naconmza 5 She'ets-She et 3 Filed April 16. 1947 I INVENTOR. HERMAN N van mm ATTORNEYS Nov. 8, 1949 H. NYGAARD nmcaznm TYPE manure nnconnnn 5 Sheets-Sheet 4 Filed April 16,. 1947 ATTORNEYS H. NYGAARD 2, 7,170

HAGAZINE TYPE MAGNETIC RECORDER 5 Sheets-Sheet-5 Nov. 8, 1949 V Filed April 16, 1947 INVENTQR HERMAN NYG/MRD BYZQMQ, W/ ATTORNEYS Patented Nov. 8, 1949 UNITED "s'rA Es- PATENT OFFICE ztuio .fifitifi'fiilif 3. :1 $1..

to Frederick Hart 8: 00., Inc Poughkeeplie,

N. 'Y., a corporation of Delaware Application April 16, 1947, Serlal No. 741,883

comma. (cam-s4) This invention relates to magnetic recorders,

and particularly to a magazine type of recorder and reproducer, in which the recording medium is contained in a casing or magazine supported on a main housing in which are mounted the magator of the equipment and which is designed to be instantly interchangeable on the recorder with other magazines, all necessary connections electromagnetic and mechanical hetween the magazine and therecorder being automatically-and correctly made in the process of positioning the magazine on the recorder. Magazines of this type are described in my copending application 'No. 741,885 filed April 16, 1947.

Rotation ofthe spools within the magazine .bythe driving mechanism draws the recording medium, preferably a paramagnetic wire, from one spool to the other, and the wire in passing from one spool to the other engages the magnetic head which extends into the magazine through an aperture provided therefor, During rotation the 2 possible the use of a magazine composed of simple castings or stampings, resulting in substantial savings in the manufacture of the magazines.

The cooperative driving and positioning mechanlsms, together with the magnetic head arrangement, make possible for the first time a magnetic recorder in which true interchangeability of the magazines can be obtained in a way suitable for use by unskilled operators.-

Within the recording unit, I have provided for a positive drive which cooperates with the magazine structure to keep a slight tension on the wire,

' eliminating slack or backlash. It thus effectively spools are carried by the driving mechanism,

which belongs to the recorder proper but which extends into the magazine to journal and position the spools for rotation free of the magazine when the magazine is emplaced on the recorder. The wire is laid evenly on the spools by a resilient guide frame which oscillates within the magazine about a pair of pivots. At thesame time the guide frame restricts the wire in its passage from one spool to the other to a path of which a portion is fixed relative to themagazine, and hence to the recorder itself, independently of the position of the guide frame. Hence the wire is always in position to engage the head, and the magazine can. be instantly emplaced on the re-. corder, regardless of the relative proportions of the wire on the two spools.

The spool-driving mechanism in the recorder is designed to cooperate with the magazine in such a way as to align the spools accurately for,

shafts or bearings in the magazine, and makes prevents breakage of the wire by sudden stresses even during frequent and rapid reversals of direction.

These and other important features of the invention may be better understood by reference to the accompanying drawings, in which a preferred embodiment is illustrated in detail. It will be understood that the invention is not limited to the exact structure shown, but may be incorporated in other equivalent forms within the terms of the appended claims.

.In the drawings:

Fig. 1 is a perspective view showing the recording and play-back unit, hereafter referred to simply as the recorder, together with the magazine mounted thereon in operating position;

Fig.2 is a perspective view'similar to that of Fig. 1 but with the magazine removed from the recorder; 1 v

Fig. 3 is a perspective view of the magazine with its cover removed, and partially broken away to show the elements of the spools which cooperate with-the recorder;

Fig. '4 -is a fragmentary transversesectional view of the top chassis plate of the recorder anddriving elements; 1 Fig. 6 is a schematic elevational view showing th spool-driving sequence during recording and,

P a i Fig. 7 is a schematic elevational view showing the spool-driving sequence during rewind;

Fig. 8 is. a top view of the driving arrangement, I

looking down on the plane indicated at line 8-8 in Fig. 5 during recording and play-back;

Fig. 9 is a bottom view of the driving mechanism in rewind position, looking up at the plane indicated at line 9-9 in Fig. 5;-

' zine.

the friction idler wheels which transmit power from the motor to the spool-driving shafts;

Fig. 11 is a plan view of the suspension of the upper friction idler wheel, showing it engaged with its driving and driven elements as it is when the record, play-back, and rewind control of the recorder is in neutral; and 1 Fig. 12 is a view similar to that of Fig. 11, but showing the lower friction idler wheel. Figs. 11 and 12 have been drawn with a line of centers joining a common element thereof to indicate the relative positions of certain parts of one figure to other parts of the other figure.

In Fig. 1 the recorder is illustrated as embodied in a single unit I, on top of which is emplaced a magazine 2 containing the recording wire. Extending from the front panel 3 is a magazine release button 4, which is pushed in to unlock the magazine 2 for removal. The frac-' tion of the total recording time or length of wire remaining on the supply spool in the magazine is shown on an indicator 5.

An off-on switch and volume control knob I is disposed in symmetrical arrangement on panel 3 with a four-position control knob 9, a screwplug type microphone connection I0, and a neon glow lamp H which flashes when the level of sound supplied is adequate for recording. An ornamental grille I2 conceals a speaker for playback purposes.

The four-position control knob 9 is arranged for recording in its first position, playing back in its second position, neutral in the third, and for rewinding in its fourth position.

trical connections for recording, play-back and rewind, such as those relating the microphone- Control knob 9, in addition to makingthe desired eleczine removed to show the cooperating mecha- I nism and the recessed seat 8 in which the magazine is emplaced. The magnetic head unit I5 is removably disposed in a head container I6 mounted on top chassis plate I'I. Head unit I5 is shapedto assist in positioning the magazine 2 while it is being seated. Frusto-conical positioning members I9 and mounted on spooldriving shafts within the recorder extend upwardly from plate I! to position the spools for rotation within the magazine upon emplacement of the magazine on the recorder. The members I9 and 20 determine the height above the recorder at which the spools are borne during rotation, freeing them from friction with the maga- Tapered studs 2|. and 22 which extend. upwardly from the members I9 and 20 engage bores within the-spools and determine the axes of rotation of the spools. The driving force which rotates the spools is transmitted by drive pins 24 and 25 which engage suitable drive bores within the spools.

During the emplacement of the magazine, the recording Wire within magazine 2 engages with the V-shaped upper engaging surfaces of the head I5, and is guided by the inclination of those surfaces through a slot into the interior of the head and into, engagement with the magnetic recording, play-back, and erasing elements.-

tellated driving head '3I engages driven means in the magazine cooperating therewith to operate a level-winding mechanism within the magazine. A lockingstud 32 secures the magazine firmly in place, until again releasedv by pressing release button 4, and spool unlocking pin 35 relzcigses the spools for rotation within the magae. The structure of the magazine interior is shown schematically in Fig. 3 with portions broken away to permit a better understanding of the functions. A cross-section of the magazine appears in Fig. 4. Magazine base plate I40 has recesses or races I4I formed therein in which the supply spool I44 and take-up spool I42 are loosely seated. The recesses are sufliciently greater in diameter than the spools so that they do not act as journals or control the axes of revolution of the spools, simply positioning them approximately. The spools fioat freely within the magazine, riding during rotation on the spool-positioning members I9 and 20 of the recorder. Resilient spring arms I45 having hardened bearing members I46 fixed therein bear upon central bearing surfaces I41 in the upper surface of the spools. These spring arms serve to hold the spools normally in their recesses without restricting their exact positioning when the magazine is emplaced on the recorder. Frusto-conical recesses I49 are formed on the underside of each spool, into which the corresponding frusto-conical positioning member I9 or 20 extending from the recorder may fit. Studs 2| and 22 engage central bores I50 within the spools to exactly fix the spools on the supporting members I9 and 20, the drive torque being transmitted by the association of the driving pins 24 or 25 with driving pin bores I5I. When the magazine is not emplaced on the recorder, spool-locking spring arms I52 bend upwardly into contact with radial grooves I54 formed peripherally in the underside of the spools I42 and I44.

When the magazine is emplaced on the recorder, the spring arms I52 are withdrawn from engagement with the radial grooves I54 so that the spools may be freely rotated. This withdrawal is effected by the engagement of an un about which the arms I52 may be forced downwardly.

The paramagnetic recording medium I60 is laid on the spools by a resilient guide frame I6I pivoted at I62 about an axis coincident with the desired path of the wire across aperture I64 for presentation to the magnetic head. The resilient guide frame I6I is formed approximately in the shape of a W with the central leg carrying an engaging arm I65 (see Fig. 4). A pulley I63 is mounted at each of the outside corners of the guide frame and the pulleys carry the wire from one spool to the pivotal axis of the guide frame, across the aperture I64, and back to the other spool. The arm I65 carries a cam-engaging member I66 which is urged by a spring I61 into contact with a screw-type cam I69 having a rightand left-handed thread closed upon itself. Cam I69 is driven from the recording and play-back I13 with the pin I10.

unit through a suitable driving, pm In and is thus caused to oscillate or rock the guide frame I8I so that the wire may be laid evenly on the spools. The path of the wire is fixed during its passage across the base plate aperture I84 however, since the front pulleys I88 are so located in the frame I8I that the pivotal axis of the guide frame is tangent to these pulleys. By presenting the wire in a fixed path in which it is engaged bythe magnetic head, which has guiding surfaces arranged to automatically direct the wire to engagement with the magnetic elements in the head, immediate interchangeability of maga-' above the top chassis plate I1 andinto the recess.

I12 in magazine base plate I80 when the magazine is emplaced. If the driving pin I happens to align itself immediately with one of the radial grooves I13 formed in the castellateddrive head- 31, it will seat therein at once. If, on the contrary, the pin I10 engages against the lands I14, drive 'head 3i will be depressed on its shaft I15 against the helical spring I18 until the head 8| has rotated sumcientlyto align a set of grooves Movement of the .head 3|. axially of shaft I15 is permitted by-a slot I11 formed diametrically therethrough and elongated axially thereof. A pin I19-fixed in head 3i and through the slot I11 transmits driving force from the shaft I15 to the head 8|, while permitting this axial movement during seating of the magazine. Thus the magazine can be placed flat against top chassis plate l1 for looking to the recorder regardless of the relative rotational positions of drive pin I10 and the drive head 3|.

The actual locking is accomplished by the entry,

and playing back, the mam leading to the takeup spool is engaged and during rewinding the system leading to thesupply spool is engaged. The spool-driving mechanism also includes, however, provisions whereby both systems are engaged while the control knob 9 is in the neutral position (in which position the drive motor is deenergized),-during the transition from recording or play-back to rewind. While the control knob is in the neutral position, the momentum of the motor armature tends to drive the two spools in opposite directions, so that they are brought to rest almost instantaneously, the wire between them being maintained taut. The frictional elements are calculated to prevent overstressing the wire so that it will not be broken.

These two power transmission systems will now be described. Referring to Fig. 5, power is supplied from a constant speed motor I00 mounted vertically in the recorder chassis below lower chassis plate 99. The motor is mounted on conventional supports designed to minimize the transmission of vibration to the chassis. The motor shaft IOI carries a pinion I02 and a fly wheel IIO. Pinion I02 is the first element in the chain leading to the take-up spool and the fly wheel I I0, which smooths out irregularities in motor speed, serves as the first element in the chain leading to the supply spool. The pinion I02 drives a spur gear. I08 which has a frictiondriving wheel I04 fixed on the same shaft. The

of locking stud 32 into a locking slot 38 in the magazine base plate.

Shaft I15 is journaled at its lower and through a lower support plate I80, and is expanded therespool-positioning member 20.

shaft of gear I03 is 99 and I1.

' In the setting of the mechanism for record-v ing and play-back, governed by the control knob 9 and shown in Figs. 6 and 8, an upper rubbertired friction idler wheel I05 is engaged between the driving wheel I04 and a take-up spool friction drive wheel I08. Take-up spool friction drive wheel I08 is freely journaled on the take-up spool drive shaft I01 which supports the take-up Shaft I01 is Journaled in the upper and lower. chassis plates I1 and 99. Shaft I01 and member 20 are caused to rotate in unison with take-up spool friction drive wheel I08 by means of a properly springloaded friction clutch I09. Proper speed reductions are introduced between drive pinion I02 into a linear winding velocity of about three feet The hub I8I is journaled in upper support plate chassis top plate I1. Pinion I85 drives a speedreducing gear I86 (Fig. 4), journaled between lower and upper support plates I80 and I84; gear I86 in turn, through an intermediate pinion I81 fixed concentrically therewith, drives a gear I89 fixed about the enlarged hub I8I, effecting a further reduction in the speed and driving cam I69 at the proper rate to lay the wire evenly on the spools within the magazine.

The mechanism in the recorder which drives thespools and the level-winding mechanism is shown schematically in Figs. 5-12. It includes a motor and two separate friction-operated power transmission systems leading therefrom, of which one communicates with the supply spool and theother with the take-up spool. During recording 75 wheel H0 and a supply spool friction drive wheel per second on the take-up spool carried by positioning member 20. The actual linear velocity will of course increase during take-up, since the radius of the windings. becomes greater as more layers of wire are laid on, while the motor speed remains constant. This does not affect sound reproduction, however, since each portion of the wire will be drawn over the magnetic head gap during play-back at a speed identical with that with which it was drawn thereover during recording.

It is necessary, after a spool of wire has had a recording made thereon, to rewind it from the take-up spool onto the supply spool before the record can be played back. The power transmission system 'leadingto the supply spool, which begins with the fly wheel H0, is engaged by turning the control knob 9 on the front of the recorder to the rewind position. The driving sequence whichmesults is illustrated in Figs. '1

and 9. Fly wheel IIO acts as a friction wheel to drive a lower rubber-tired friction idler wheel II2. Idler wheel H2 is engaged between fly journ-aled' in chassis plates 7 H4. Supply spool friction drive wheel H4 is iournaled on the shaft II! which supports the supply spool-positioning member I and engages therewith through the spring-loaded friction clutch H0. The clutches I09 and H0 are adjusted toslip at a torque substantially below that corresponding to the breaking strength of the wire applied to either one of the spools for any number of layers of the wire on the spools, so that there is no possibility of breakage of the wire, even upon rapid reversals of the direction of wire travel' The means by which the recorder is shifted from recording or playing back to rewinding is shown in Figs. 5, 8, 9, 10, 11 and 12. This consists essentially of a linkage operated from the control knob 0 on the front of the recorder which alternately engages the idler wheels I and H2 and which operates to engage them both while knob 3 is in neutral, so as to effect a stopping and reversal in the rotation of the spools and direction of wire travel without either breaking the wireor allowing slack to develop therein. The upper and lower idler wheels I05 and H2, which serve respectively to transmit power from the driving wheel I04 to the take-up spool friction drive wheel I03 and from the motor fly wheel I I0 to the supply spool friction drive wheel position of the tie rod I23 when the control kn 0 is In neutral.

In this third equilibrium position of the tie rod I23 the pin I32 engages neither of the levers I2I nor I22. They are urged into opposite rotations, however, by the spring I3I, and so cause engagement of their respective idlers with the driving and driven elements thereof. The spacing of these elements, namely the two spool friction drive wheels, the motor fly wheel and the driving wheel I04, and the size of the idlers and dimensioning of their suspensions is such that with no stress exerted upon the levers I2I and I22 by the tie rod I23, the slots I33 and I34 overlie each other allowing slack within which the pin I32 may move either way before bringing up against the end of one of the slots I33 or I34. The relation of these elements in neutral is illustrated in Figs.

11 and 12, where both idlers are shown engaged to bear against the end of the slot I34 in lever I22 and rotates lever I22 counterclockwise, thus posi- II4, are pivoted for free rotation in a horizontal plane in the mouths of a pair of yokes H3 and I2I. This construction is best shown in Fig. 10. The yokes H3 and I20 are pivoted respectively on two levers I2I and I22, shown in plan in Figs. 11 and 12. The levers I2I and I22 are freely journaled for rotation about a vertical shaft I24 which is fixed in the chassis plates I1 and 33. A coil spring I3I wound about the shaft I24 and engaging the levers I2I and I22 urges them into opposite rotations, lever I2I counterclockwise and lever I22 clockwise when seen from above, as in Figs. 11 and 12. Rotation of the levers I2I and I22 shifts the idler wheels I00 and H2 to the right or left, in order to engage them with the spool friction drive wheel and driving wheel I04 or motor fly wheel, as the case may be, with which they are coplanar.

Rotation of the levers I2I and I22 is governed by a tie rod I23. This tie rod carries on its end a pin I32 which engages with a slot I33 in the upper lever I2I and with a slot I34 in the lower lever I22. The slots I33 and I34 are open in opposite directions, so that motion of the tie rod I23 to the right draws lever I22 into counterclockwise rotation and motion of the tie rod to the left pushes the lever I2I into clockwise rotation. Because of the tension exerted by the coil spring I3I, however, rotation of either lever as compelled by tie rod I23 is followed by rotation of the other lever in the same direction,

within the limits imposed by the spool drive friction wheels, against which the idler wheels bring up.

Tie rod I23 is connected to a crank I35 depending from a spring-loaded shaft I33 (Fig. 5).

Shaft I33 is connected by conventional means to the control knob 9 on the front panel of the tively withdrawing the lower idler wheel I I2 from engagement between the motor fly wheel and the supply spool friction drive wheel II4. Engagement of the upper idler wheel I05 between the driving wheel I04 and the take-up spool friction drive wheel I03 is provided solely by the tension of coil spring I3I. The pin I32 of tie rod I23 is drawn away from the end of slot I33 in the upper lever I2I, lever I2I being prevented from fully following the rotation of lower lever I22 by the engagement of the upper idler I05. I

Conversely in rewind position, the tie rod I23 is drawn to the left and held in the second of the above-mentioned equilibrium positions. In assuming this position the tie rod I23 brings the pin I32 to bear against the end of slot I33 in lever I2I and rotates the latter clockwise, thus positively disengaging-the upper idler wheel I05 from the take-up spool friction drive wheel I 03. The lower idler wheel H2 is engaged between motor fly wheel H0 and supply spool friction drive wheel I I4 by the tension of coil spring. I3I. Similarly, during rewinding the lower idler engages and prevents the lower lever I22 from fully following the rotation of the upper lever I 2I which is compelled by the tie rod. It is to be noted thus that engagement of the idler wheels is not effected by pressure of the tie rod against the lever I2I or I22 of the idler in question, but that the tie rod eflects primarily disengagement of the idler against whose lever it abuts.

On the changeover from record or play -back to rewind, the motion of the tie rod I23 towards neutral, with which the changeover begins is followed by the lever I22 against which the pin I32 is stressed until the disengaged idler II2 brings up against the fly wheel I I0 and the supply spool friction drive wheel I I4. The pin I32 then leaves contact with the end of the slot I34 in lever I22 and moves across the overlapping space of the two slots. Simultaneously the power to the motor is shut off by means of a switch associated with the control knob 9. Both idlers are now engaged and both spool friction drive wheels I03 and H4 are driven in opposite directions by the momentum of the motor armature. The clutches I03 and H3 slip and the spools come rapidly to rest 70 with the wire between them remaining taut. As

.\ the tie rod I26 continues its'motio'n towards the rewind position, the pin I32 brings up against the larly on the changeover from rewind to record or play-back, the take-up spool friction drive wheel takes hold before the supply spool friction drive wheel is disengaged. 1

I- claim: v

1. In a magnetic recorder, a housing, a motor mounted therein having a vertically disposed motor drive shaft, spool-positioning and driving means extending from said housing,fin cluding a supply spool shaft, 9. first driven friction wheel rotatably disposed about said supply spool shaft, a first friction clutch arranged to fix said first driven friction wheel against rotation relative to said supply spool shaft; a take-up spool shaft, a second driven friction wheel rotatably disposed about said take-up spool shaft, a second friction clutch arranged to fix said second driven friction wheel against rotation relative to said take-up spool shaft; means for driving said first and second driven friction wheels from said motor, comprising a fly wheel arranged to act as a first friction driving wheel, a motor drive pinion mounted on the shaft ofsaid motor, a spur gear arranged to mesh with said motor drive pinion and having a second friction driving wheel affixed thereto, a lower idler friction wheel mounted in said chassis on a first doubly-articulated mount and arranged to be shifted into engagement between said first friction driving wheel and said first driven friction wheel, an upper idler friction wheel mounted in said chassis on a second doubly-articulated mount and arranged to be shifted into engagement between said second friction driving wheel and said' second driven friction wheel, spring means connecting said first and second mounts and urging them in mutually opposite directions for engagement of their idler friction .wheels with their respective driving and driven friction wheels, whereby during such engagement said mounts assume a position of equilibrium under the influence of said spring;

therebetween of said linkage means so that on the change-over from one displacement of said linkage means to the other both idler friction wheels are engaged during the passage of said linkage across said slack. f

2. In a magnetic recorder employing a closed magazine for the storage of a paramagnetic recording medium, means to drive alternately and in opposite directions for the recording or playback and rewinding respectively of the recording medium, either of two positioning and driving members extending from said recorder for engagement with the spools in said magazine, comprising a chassis adapted to accommodate the magazine for rotation of the spools therein, motor means arranged on said chassis, two friction drivin'g wheels disposed in said chassis on spaced apart parallel shafts and driven in opposite dire'ctions by said motor means,- two spaced apart parallel spool-driving shafts arranged in said chassis, a driven friction wheel freely journaled on the first of said spool-driving shafts, a driven friction wheel freely journaled on the second of said spool-driving shafts, slipping clutches frictionally engaging said driven friction wheels with tion wheels permitting their translation relative to said chassis, stressed spring means connecting said mountings and therethrough urging said idler wheels in opposite directions so as to engage them with their respective driving and driven friction wheels, said engagement establishin an equilibrium position for said mountings under the infiuence of said spring means, linkage means loosely engaging said mountings and adapted for alternate positive abutment against each of said mountings in directions opposite to those in which said mountings are respectively urged by said spring means, whereby motion of said linkage means disengages the mounting against which it abuts and by further stressing of said spring means tightens the engagement of the mounting against which it does not abut, and slack between said linkage means and the surfaces of said mountings against which said linkage means abuts while in the said equilibrium position, whereby on the change-over from abutment of said linkage means against one of said mountings to abutment against the other mounting both .idler wheels are allowed to come into engagement with their respective driving and driven friction wheels under the influence of said spring means.

3. In a magnetic recording and reproducing device arranged for the interchangeable appli-. cation thereto of magazines containing a para-- magnetic medium wound on and extending between supply and take-up spools, a motor, means for transmitting power from said motor to supply and ,take-up spool-driving shafts, comprising a fiy wheel driven by said motor, a first intermediate idler friction wheel arranged to engage said fly wheel, a supply spool shaft, a first driven fric=- tion wheel journaled rotatably about said supply spool shaft, and clutch means arranged to connect said supply spool shaft to said first driven friction wheel; a pinion driven by said motor, a gear meshing with-said pinion, a friction drive wheel affixed to said gear, a take-up spool-shaft, a second driven friction wheel journaled rotably on said take-up spool shaft, clutch means for said-fly wheel and said first driven friction wheel' and disengagement of the other thereof, to a position of engagement of the other thereof between said friction drive wheel and said second driven friction wheel and disengagement of the first thereof, said shifting means being arranged to apply driving force simultaneously to both of said driven friction wheels during the shifting of said chassis and adapted to be driven in opposite directions by said motor means, a pair of spaced apart spool-driving shafts, spool-posh timing and driving means fixedly mounted on said spool-driving shafts, .driven friction wheels journaled on said spool-driving shafts, slipping clutches frictionally engaging said driven friction wheels with their respective spool-driving shafts, two friction idler wheels journaled on separate axles and adapted to be separately frictionally engaged between said driving and driven friction wheels so as to transmit motion therebetween, mountings for said idler wheels pivotally mounted in said chassis and permitting translation of said idler wheels relative to said chassis, stressed spring means connecting said mountings and urging mutually opposite motions thereof so as to. engage said idler wheels with their respective driving and driven friction wheels, linkage means loosely engaging said mountings so as to transmit motion thereto in directions respectively opposite to-those in which said mountings are urged by said spring means, whereby said' linkage means effects by motion in one direction disengagement of one of said idler wheels and resilient engagement of the second with its driving and driven friction wheels, and by motion in the opposite direction effects disengagement of the second of said idler wheels and resilient engagement of the first of said idler wheels, with its driving and driven friction wheels.

5. In a magnetic recorder employing a recordinglmedium wound upon two spools in a maga-' zine, spool-driving means comprising a chassis, two spaced apart parallel spool-driving shafts mounted in said chassis, a first friction driving wheel mounted in said chassis for rotation in a first plane perpendicular to said spool-driving shafts, a second friction driving wheel mounted in said chassis for rotation in a direction opposite to that of said first friction driving wheel in a second plane parallel to said first plane, a driven friction wheel journaled on one of said spool-driving shafts for rotation substantially in said first plane, a driven friction wheel joumaled on the other'of said spool-driving shafts for rotation substantially in said second plane, slipto said spool-driving shafts, two spaced apart levers journaled for rotation about said axle, spring means engaging saidlevers and ur in them into mutually opposite rotations, a y pivoted on each of said levers for rotation in a plane perpendicular to said axle, idler wheels pivotally mounted in the mouths of said yokes for rotation in said first and second planes respectively, linkage means connecting said levers and restraining their mutually opposite rotations, the diameter and spacing of said friction driving wheels and driven friction wheels and the diameter of said idler wheels being so chosen that rotation of said levers by means of said linkage engages alternately one and the other of said idler wheels with its respective driving and driven friction wheels.

6. In a magnetic recorder employing a closed magazine containinga paramagnetic recording medium wound upon and extending between two spools, driving means adapted to transfer said medium from one to the other of said spools and ping clutches frictionally engaging said driven go friction wheels with their respective spool-driving shafts, an axle fixed in said chassis parallel back comprising a driving chassis adapted to accommodate the magazine for rotation of the spools therein, spaced apart spool positioning and driving shafts extending from the chassis for engagement with said spools within the magazine, driven friction wheels mounted on said shafts for rotation independently thereof. slippin clutches frictionally engaging said driven friction wheels with said shafts, a drive motor mounted on the chassis, a friction drive wheel on the axle of said motor, a second friction drive wheel axially displaced from said motor and driven in the opposite direction thereby through reduction gearing, two friction idler wheels journaled on separate parallel axles and susceptible of motion in the planes of their rotation along a path intermediate the line of centers of said shafts and the line of centers of said motor and said second friction drive wheel, and linkage meansloosely connecting said idler wheels, whereby motion ofsaid linkage means in one direction effects frictional engagement of one of said idler wheels with the friction drive wheel on the axle of said motor and with one of saiddriven friction wheels and motion of said linkage means in the opposite direction effects frictional engagement of the other of said idler wheels with said second friction drive wheel and the other of said driven friction wheels.

HERMAN NYGAARD;

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

